The exemplary embodiment relates to fusing. It finds particular application in conjunction with a fusing device for an electrophotographic image forming apparatus and will be described with particular reference thereto. However it will be appreciated that the device finds application in other fusing and curing systems, such as solid-ink transfix or fusing systems.
In typical electrophotographic image forming devices, such as copy machines and laser beam printers, a dry marking material, such as toner particles adhering triboelectrically to carrier granules, is used to create an image on a photoconductive surface which is then transferred to a substrate, such as paper. The toner image is generally fused to the substrate by applying heat and pressure to melt or otherwise fuse the dry marking material. The fusing device includes a fuser roll which fuses the toner onto the paper, and a pressure roll which presses the paper against the fuser roll. The fusing process generally serves two functions, namely to attach the image permanently to the sheet and to achieve a desired level of gloss.
Conventionally, heat sources such as halogen lamps have been used as heat sources for the fuser roll. The halogen lamp heats the surface of the fuser roll to a target temperature with radiant heat. Heat pipe fuser rolls, which use a heated working liquid to apply heat from within the fuser roll, can have advantages over radiant heated rolls in that they tend to provide a more even distribution of heat across the fuser roll surface.
To function efficiently, the interior of a heat pipe fuser roll is evacuated to a low vacuum and filled with the working liquid to ensure that substantially no air is present. A typical assembly process usually involves multiple steps, each step being performed by a manufacturer with the particular expertise and equipment necessary to complete the step. As a consequence, heat pipe fuser rolls are often shipped several times during their manufacture, adding considerably to their cost and preparation time. For example, a typical process begins with the fabrication of a heat pipe by a heat pipe vendor, which is evacuated to about negative 3 Torr and sealed before shipping to an imaging device vendor. The imaging device vendor may machine the surface of the heat pipe to meet specifications. A fuser coating or number of coatings may be applied to the exterior of the heat pipe. After forming the surface layer, the assembled fuser roll is returned to the heat pipe vendor for backfilling with a working liquid, such as water. Because of the high temperatures used in forming the conformable surface layer, the water would burst the heating pipe if introduced before the coating is formed. Accordingly, the surface layer forming stage is performed with the heat pipe under vacuum.